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Parys Mountain EarthCache

Hidden : 09/02/2008
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Geocache Description:

This impressive chasm was opened up at an early stage of mining after the collapse of workings reached by numerous shallow shafts.


This impressive chasm was opened up at an early stage of mining after the collapse of workings reached by numerous shallow shafts. It was a feature much marvelled at by visitors and has been recorded in several early paintings. These show projecting platforms with windlasses, and miners working the ore from the sides, suspended on ropes. Most of this opencast was worked by the Parys Mine, the smaller "Hillside Opencast" to the east being worked by the Mona Mine. The opencasts represent only a small proportion of the mine as later extraction occurred through shafts that reached depths of 300m, some 130m below sealevel and now therefore flooded. Since the rocks dip steeply to the north, most of these deeper underground workings are located between the Opencast and the main road over the mountain. The small lake at the bottom results from the damming of a deep level draining to the north. The water is very acidic (sulphuric acid - pH 2) and meant that pumps had to be made from oak, not iron. Its orange-brown colour is due to the very high concentrations of iron (ferric - in solution) leached from oxidising sulphide minerals, as indeed do the range of yellows, reds and purples in the spoil. This dramatic scene has been used in numerous films from "Dr Who" to, most recently, "Mortal Kombat 2".


The buildings on the south side of the Opencast are the remains of the Mona Mineyard. This group of offices,smithy and stores, surrounding a courtyard,was the focus of the mine's surface activities. Here miners bought their tools, candles and explosives from the Mona Mine company, and bid in small groups at auctions for "bargains" to work underground sections of the mine for a fortnight. The equivalent mine yard for the Parys Mine is at the south west corner of the Opencast, but its buildings are in a more ruinous state.


It was discovered that purer metal could be obtained very efficiently by precipitation from solution. Water was pumped to the top of the mountain and allowed to drain down through the spoil and the underground workings (i.e. "sparging"), dissolving the copper due to its very acid nature. Scrap iron was then added to the copper-rich water to give metallic copper in a sequence of purpose-built, brick-lined "precipitation ponds" of which there are several examples on the mountain, the best preserved being those in this central valley. The dissolved iron was itself then oxidised and precipitated as ochre, a valuable by-product that was marketed as a pigment.


This distinctive building, prominent on the skyline at the east end of the mountain, once housed a Cornish Beam Engine. It was one of the earliest steam engines in north Wales, installed in 1819 to pump water from the adjacent 230m Pearl shaft. 4Its chimney stood at the north west corner, but sadly it collapsed some years back. In front are the remains of a capstan pit used to raise and lower the oak pump rods in the shaft.


In this large area of spoil, just to the north of the mass of hard quartz-rich rock known as "Carreg y Doll", traces of a "dressing" or "cobbing floor" can be seen in the form of a cobbled surface, sadly now much reduced by the removal of spoil for road stone. This is where the ore from Mona Mine was broken up into small pieces by the famous "Copper Ladies" (Morwynion Amlwch) using an iron flat hammer, and protecting their fingers with iron rings. The ore fragments were then picked out by children and roasted in large heaped kilns for up to 3 months, filling the air with fumes.


Built in 1878 on the summit of Parys Mountain, in the hope of reducing operating costs, the windmill was used to pump water from the underlying mine workings. It was later connected to a steam engine at the nearby 270m deep Cairns shaft by a system of reciprocating wooden rods ("flat rods"), the remains of which could clearly be seen during the early part of this century. The windmill was unique amongst the many on Anglesey in that it comprised five sails. To the north lies Oxen Quarry which owes its name to annual celebrations of the first major rediscovery of rich copper ores on March 2nd 1768. On this day the people of Amlwch were treated to a roasted oxen. Within this quarry, the early miners discovered "ancient" spoil tips. These contained rounded stones, or "mauls", that had been used as hammers, and charcoal from "firesetting", an early technique used to shatter rock before black powder explosives became available in the 18th century. The charcoal has been dated by carbon-14 to nearly 2000 years B.C. The history of copper mining on the mountain thus goes back to the Early Bronze Age, making it one of the earliest mines known in Britain.


The 4000 years of mining history continues today. Anglesey Mining plc was formed in 1984 to explore and develop the Parys Mountain property. In 1988 it raised £5.5 million and sank a shaft to a depth of 300m with more than 1 km of underground tunnelling. Over 2,000 tonnes of ore were mined, processed and sold, but development was halted by poor market conditions. Geological investigation recommenced in 1995 and led to further drilling from surface in 1997 with the objective of increasing the company's current resource of 6.5 million tonnes at a combined grade of >1 0% zinc (the principle product), copper, lead, silver and gold. The planned mine would require over 100 employees and should operate for more than 15 years. Ore would be extracted from 80-600m below surface, concentrated in a processing plant and then despatched to a smelter.


It was not until the mid-eighteenth century that the first major ore deposit of the modern industrial era (the "Golden Venture Lode") was discovered by Jonathan Roose. His tombstone and eulogy may be seen today in Amlwch churchyard. At this time the mountain was divided between two owners leading to the development of adjoining mines, the Mona Mine to the East (owned by an ancestor of the present Marquess of Anglesey) and Parys Mine to the West. The copper from these two mines dominated the world's markets in the 1780s. It was used to sheath the admiralty's ships of war, in order to prevent the growth of seaweed and barnacles and to prevent boring by worms. This increased their manoeuvrability and made possible Nelson's victories. The post-war slump and diminishing accessible ore reserves, together with competition from cheaper ores from' abroad, led to the decline of the mines and to the end of deep mining in the 1880s. The ore was initially worked on the surface from shallow shafts and then by open-pit mining (Opencasts) and later underground from adits and from shafts up to 300m deep. The ore was broken into small lumps by hand, the best ore being transported by ship from Amlwch Port to Lancashire or South Wales for smelting. Copper was concentrated and extracted from the remainder using kilns and furnaces on site and at Amlwch Port itself. It was also discovered that purer metal could be obtained efficiently, although in small amounts, by its precipitation from drainage water with scrap iron in purpose-built ponds. Associated with the mines, other important chemical industries were established on the mountain based on by-products, such as ochre pigments, sulphur, vitriol and alum. The eighteenth century miners recognised that they were following in the steps of much earlier workers, an observation that was linked to the discovery locally of copper ingots bearing Roman inscriptions. Recently, excavations have enabled surface debris to be dated to nearly four thousand years ago, (the early Bronze Age), and access has also been regained to the sealed.


The rocks of Parys Mountain originated as muds in the margins of a sea basin around 440 million years ago. At that time submarine volcanoes were erupting lavas and ashes, and the fumes they exhaled produced rich deposits of metals on the sea floor. These metals occur as the sulphide minerals chalcopyrite (copper and iron), galena (lead), sphalerite (zinc), with abundant pyrite (iron), and they form an ore deposit ("Kuroko type") which is unique in Britain. During later distortion of the earth's crust (the "Caledonian Orogeny" circa 400 million years ago) the ore deposit was deformed by being tilted steeply down to the north, folded (synclinal structure) and fractured (faulting), although this interpretation is currently under revision. During these phases of deformation some of the metals were remobilised, giving rise to a complex ore body. The weathering of this deposit has produced very acidic conditions (pH @ 2). The abundant iron has been redeposited in different forms to give the striking red and brown colours of the mountain: there is little surface sign of copper today, but lead was redeposited as its sulphate ("anglesite") for which Parys Mountain is the type locality. This extreme, harsh, acidic setting has resulted in a unique environment supporting unusual forms of life. Special bacteria derive their energy from the oxidation of sulphides, and a rich flora of special lichens can be found coating rock surfaces, whilst heather survives over most of the mountain. Bats, including the rare lesser horse shoe bat, have colonised the mine workings, and amongst the birds to be seen soaring with the jackdaws over the opencasts are the red-legged / billed choughs.

To log the cache please upload a photograph of you or you GPSr with the mine in the back ground and E-Mail me the answers the following questions.

1) What gives the rocks it reddish colour.

2) Estimate the depth of the opencast

3) Estimate the width of the opencast from left to right from the information board .

Any logs with no photograph may be deleted

Additional Hints (No hints available.)